[dconf] Fix crash when user database is not present

[Ryan Lortie <ryanl src gnome org>]

commit c80896f5644ec0a07822047dd7e899da63b42e89
Author: Ryan Lortie <desrt desrt ca>
Date:   Sun May 8 14:08:38 2011 +0200

    Fix crash when user database is not present
    
    If we fail to open the database in the user's home directory then the
    variable will be NULL.  The refactor of the read function for lockdown
    support missed this check, resulting in a rather dramatic crash on fresh
    accounts.

 engine/dconf-engine.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/engine/dconf-engine.c b/engine/dconf-engine.c
index ec99116..087d780 100644
--- a/engine/dconf-engine.c
+++ b/engine/dconf-engine.c
@@ -452,7 +452,11 @@ dconf_engine_read_internal (DConfEngine  *engine,
       break;
 
   while (i < limit && value == NULL)
-    value = gvdb_table_get_value (engine->gvdbs[i++], key);
+    {
+      if (engine->gvdbs[i] != NULL)
+        value = gvdb_table_get_value (engine->gvdbs[i], key);
+      i++;
+    }
 
   g_static_mutex_unlock (&engine->lock);